Aerosol generation

ABSTRACT

A method for aerosolising a liquid comprises the steps of: —providing an aperture plate having at least 100 outlet holes per mm; delivering liquid to the aperture plate; and vibrating the aperture plate to produce an aerosol. The viscosity of the liquid is in the range of from 1 to 15 cP and the surface tension of the liquid is in the range of from 72 to 0.5 mN/m. The output rate of the generated aerosol is greater than 0.01 mL/min.

FIELD OF TECHNOLOGY

This invention relates to aerosol generators.

BACKGROUND

Vibrating aperture plates are used in a wide range of aerosol devices, and are typically supported around their rims by a vibrating support which is vibrated by a piezo element. Also, aerosol devices may have passive or static aperture plates, which operate for example by an acoustic signal from a horn causing a stream of medication to be filtered through the aperture plate.

Aerosol generators comprising a vibratable member and plate body operably coupled to the vibratable member are known. The plate body has a top surface, a bottom surface, and a plurality of apertures extending from the top surface. The apertures may be tapered such that when a liquid is supplied to one surface and the aperture plate is vibrated using the vibratable member, liquid droplets are ejected from the opposite surface. Details of such known systems are described for example in U.S. Pat. No. 6,235,177, US2007/0023547A, and U.S. Pat. No. 7,066,398, the entire contents of which are herein incorporated by reference.

Currently, aperture plates are produced by a variety of different means, including electroplating and laser drilling. Electroplating is generally the most advantageous production method from a technical and economic standpoint. U.S. Pat. No. 6,235,177 (Aerogen) describes an approach based on electroplating, in which a wafer material is built onto a mandrel by a process of electro-deposition where the liquefied metals in the plating bath (typically Palladium and Nickel) are transferred from the liquid form to the solid form on the wafer. Material is transferred to the conducting surface on the mandrel and not to the photo resist areas which are non-conducting. Areas are masked with non-conductive photo resist where metallic build-up is not required. After the conclusion of the plating process, the mandrel/wafer assembly is removed from the bath and the wafer peeled from the mandrel for subsequent processing into an aperture plate.

However, a problem with this approach is that the hole size is dependent on the plating time and the thickness of the resulting wafer. The process can be difficult to control, and if not perfectly controlled some holes may be near closed or blocked, or over-sized, and there may be out-of-tolerance variation in the sizes of the holes Also, there are limitations on the number of holes per unit of area. Further, with this technology an increase in output rate usually requires an increase in particle size, which generally may not be desired.

STATEMENTS OF INVENTION

The invention provides a method for aerosolising a liquid comprising the steps of:—

-   -   providing an aperture plate having at least 100 outlet holes per         mm²;     -   delivering liquid to the aperture plate wherein the viscosity of         the liquid is in the range of from 1 to 15 cP and the surface         tension of the liquid is in the range of from 72 to 0.5 mN/m;         and     -   vibrating the aperture plate to produce an aerosol wherein the         output rate of the generated aerosol is greater than 0.01         mL/min.

In some cases the fraction of the droplets which are less than 3 microns in size is greater than 75%, greater than 80%, greater than 85%, or greater than 90%.

In some embodiments the aperture plate has at least 500 outlet holes per mm², at least 1,000 outlet holes per mm², at least 1,500 outlet holes per mm², at least 2,000 outlet holes per mm², at least 2,500 outlet holes per mm², at least 3,500 outlet holes per mm², or at least 5,000 outlet holes per mm².

In some embodiments the volumetric median diameter of the droplets is less than 5 microns, less than 4 microns, less than 3 microns, less than 2.5 microns, less than 2.0 microns, less than 1.5 microns, or less than 1 microns.

In some cases the viscosity of the liquid is less than 12 cP, less than 10 cP, less than 7 cP, less than 5 cP, or less than 2 cP.

In some embodiments the surface tension of the liquid is less than 70 mN/m, less than 65 mN/m, less than 60 mN/m, less than 55 mN/m, less than 50 mN/m, less than 40 mN/m, less than 30 mN/m, less than 25 mN/m, less than 20 mN/m, less than 10 mN/m, less than 5 mN/m, or greater than 0.5 mN/m.

The output rate of the generated aerosol in some cases is greater than 0.05 mL/min, greater than 0.075 mL/min, greater than 0.1 mL/min, greater than 0.2 mL/min, greater than 0.3 mL/min, greater than 0.33 mL/min, greater than 0.5 mL/min, greater than 1.00 mL/min, or greater than 2.00 mL/min.

In some embodiments there is provided a method for aerosolising a liquid comprising the steps of:—

-   -   providing an aperture plate having at least 100 outlet holes per         mm²;     -   delivering liquid to the aperture plate; and     -   vibrating the aperture plate to produce an aerosol comprising a         plurality of droplets in which     -   the fraction of the droplets which are less than 3 microns in         size is greater than 75%.

In one case the fraction of the droplets which are less than 3 microns in size is greater than 80%, greater than 85% or greater than 90%.

In some embodiments the aperture plate has at least 500 outlet holes per mm², at least 1,000 outlet holes per mm², at least 1,500 outlet holes per mm², at least 2,000 outlet holes per mm², at least 2,500 outlet holes per mm², at least 3,500 outlet holes per mm², or at least 5,000 outlet holes per mm².

In some embodiments the volumetric median diameter of the droplets is less than 3 microns, less than 2.5 microns, less than 2.0 microns, less than 1.5 microns, or less than 1 microns.

In some embodiments the viscosity of the liquid is less than 2 cP, less than 5 cP, or less than 10 cP.

In some embodiments the surface tension of the liquid is less than 60 mN/m, less than 50 mN/m, less than 40 mN/m, less than 30 mN/m, less than 25 mN/m, less than 20 mN/m, less than 10 mN/m, less than 5 mN/m, or greater than 0.5 mN/m.

In one case the surface tension of the liquid is in a range between 72 mN/m to 0.5 mN/m and the viscosity is within a range from 1 to 10 cP.

In some embodiments the output rate of the generated aerosol is greater than 0.1 mL/min, greater than 0.2 mL/min, greater than 0.3 mL/min, greater than 0.33 mL/min, greater than 0.5 mL/min, greater than 1.00 mL/min, or greater than 2.00 mL/min.

The liquid may contain a medicament, a surfactant or a pharmaceutical.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a wafer prior to doming;

FIG. 2 is a view of an aperture plate formed by doming the wafer of FIG. 1 ;

FIG. 3 is a plot of particle size vs cumulative volume and volume frequency of an aerosol according to the invention;

FIGS. 4A and 4B are plots showing a comparison of droplets size of a surfactant type formulation generated using photodefined technology (bottom) and plating defined technology (top);

FIGS. 5A and 5B are plots showing a comparison of fine particle fraction less than 5 microns for a surfactant type formulation generated using photodefined technology (bottom) and plating defined technology (top); and

FIGS. 6A and 6B are plots showing a comparison of fine particle fraction less than 3 microns for a surfactant type formulation generated using photodefined technology (bottom) and plating defined technology (top).

DETAILED DESCRIPTION

FIG. 3 shows a droplet size (volumetric median diameter, VMD) of a surfactant type formulation generated using the photodefined technology.

Dv(50) [VMD] for this drug/device combination was recorded as 1.048 microns.

Geometric standard distribution (GSD) for this drug/device combination was recorded as 1.925.

Aerosol output rate for this drug/device combination was recorded as 0.33 ml/min.

FIGS. 4A and 4B show a comparison of droplet size via laser light scattering (commonly known as Volumetric Median Diameter (VMD)) [Ref: ISO13320 Particle Size Analysis 2-laser diffraction method and FDA Guidance (1993): Reviewer Guidance for Nebulizers, Metered Dose Inhalers, Spacers and Actuators. Available from http://www.fda.gov/downloads/medicaldevices/deviceregulationandguidance/guidancedocuments/u cm081293.pdf] of a surfactant type formulation generated using the photodefined technology (4 b) and existing plating defined mesh nebulisers (4 a). It will be noted that the X-axis scales are aligned to demonstrate shift of population to the right (i.e. low droplet size) for the photodefined technology.

FIGS. 5A and 5B show a comparison of fine particle fraction (FPF) less than 5 microns, for a surfactant type formulation generated using the photodefined technology (5 b) and existing plating defined mesh nebulisers (5 a). It will be noted that the X-axis scales are aligned to demonstrate shift of population to the right (i.e. low droplet size) for the photodefined technology.

FIGS. 6A and 6B show a comparison of fine particle fraction (FPF) less than 3 microns, for a surfactant type formulation generated using the photodefined technology (6 b) and existing plating defined mesh nebulisers (6 a). It will be noted that the X-axis scales are aligned to demonstrate shift of population to the right (i.e. low droplet size) for the photodefined technology.

The invention utilises photodefined technology as described in WO2012/092163A and our WO2013/186031A (the entire contents of both of which are incorporated herein by reference) to provide an aperture plate having at least 100 outlet holes per mm². Liquid is delivered to the aperture plate and the plat is vibrated to produce an aerosol.

A domed aperture plate 40 is illustrated in FIG. 2 . FIG. 1 shows the wafer 30 formed from a plating material 31 with a reservoir layer having apertures 32 and an outlet layer having outlet apertures 33.

Example 1

The specific aperture plate used to aerosolise a surfactant type formulation as described above had the following reservoir and outlet layer characteristics: the reservoir layer had holes of diameter 36 μm, a layer thickness of 40 μm and a hole pitch of 100 μm. The outlet layer had holes of diameter 1 μm, layer thickness of 5.2 μm and a hole pitch of 7.5 μm. It was driven using a controller at 20 V.

Example 2

Colistin at 0.5-1.5 ml/min with a volumetric median diameter of 4-5 μm was nebulised using an aperture plate with an outlet layer thickness of 6.8-7 μm, an inlet hole diameter of 2.0-2.10 μm (on the outlet layer) and an outlet hole diameter of 2.5-2.55 μm (also on the outlet layer). These holes were spaced at a pitch spacing of 8.46 μm. The reservoir holes on the inlet layer were 50 μm and spaced at 100 μm apart. The total aperture plate thickness was 60-62 μm. This device was driven between 108-128 kHz and at 12-15 V on the drive controller which created a maximum amplitude on the vibrating plate of 1.5-3 μm.

Example 3

To determine the effect of increasing viscosity and decreasing surface tension on aerosol generation, a series of standards were made by diluting neat glycerol with 0.9% saline, and diluting ethanol with purified water. The ratios of the dilution ranged from 0-100% w/w. Each solution was characterised for viscosity and surface tension. The results are shown below (Table 1 & 2). The instrument used to measure viscosity was a Viscometer (Brookfield Viscometer (DV2TLV)) unless referenced. The instrument used to measure surface tension was an optical tensiometer (OneAttension Theta) using a pendant drop experiment method unless referenced. [Ref: Lide, D. R., 1992., CRC Handbook of Chemistry and Physics, 73^(rd) ed. Boca Raton; Ann Arbor; London: CRC]

Example 4

The aperture plates used to aerosolise a respirable medication type formulation as described above was manufactured from an alloy of Palladium and Nickel using photodefined technology and had the following reservoir and outlet layer characteristics: the reservoir layer had holes of diameter 50 μm, a layer thickness of 58 μm and a hole pitch of 100 μm. The outlet layer had holes of diameter between 2.5-3 μm, layer thickness of 6.5 μm and a hole pitch of 16 μm. It was driven using a controller at 13 V.

Example 5—Comparative

The aperture plates used to aerosolise a respirable medication type formulation as described above comprised of a single electroplated layer structure of an alloy of Palladium and Nickel with the following characteristics: 210 holes per linear inch, a layer thickness of 60 μm, a hole pitch of 121 μm, the inlet hole of diameter 80 μm, the outlet holes of diameter between 3-5 μm. It was driven using a controller at 12 V.

Viscosity

TABLE 1 Viscosity of various concentration of Glycerol and Ethanol (at 25° C.) [Ref: Lide, D. R., 1992., CRC Handbook of Chemistry and Physics, 73^(rd) ed. Boca Raton; Ann Arbor; London: CRC] Glycerol Viscosity Ethanol Viscosity (% w/w) (cP) (% v/v) (cP) 0 0.89 0 0.89 5 1.01 10 1.32 10 1.15 20 1.81 20 1.54 40 2.35 40 3.18 60 2.24 60 8.82 80 1.75 80 45.9 100 1.07 100 934

Surface Tension

TABLE 2 Surface tension of various concentration of Glycerol (at 18° C.) and Ethanol (at 20° C.) [Ref: Lide, D. R., 1992., CRC Handbook of Chemistry and Physics, 73^(rd) ed. Boca Raton; Ann Arbor; London: CRC] Glycerol Surface tension Ethanol Surface tension (% w/w) (mN/m) (% alcohol) (mN/m) 5 72.9 5 — 10 72.9 10 — 20 72.4 24 — 30 72 34 33.24 50 70 48 30.1 85 66 60 27.56 100 63 72 26.28 80 24.91 96 23.04

2) Commercially Available Pharmaceutical Formulation

TABLE 3 Measured Surface tension and Viscosity of various pharmaceutical formulations Surface Tension Viscosity Product (mN/m) (at 20° C.) (cP) (at 18° C.) Colistimethate sodium 41.49 2.87 Curosurf ® Surfactant 24.34 10.58 Alveofact ® Surfactant 23.40 12.19

The aperture plates (cores) described in Example 4 (photodefined technology) were used to aerosolise various formulations as described below. All Example 4 devices were manufactured from the same wafer.

The results shown in Table 4, are the average flowrate (n=3) for increasing % w/w of Glycerol and % v/v of Ethanol.

The flowrate was determined by measuring the time to nebulise a 250 μL dose using a stopwatch and the data inputted into the formula below to give the flowrate.

${{Aerosol}{Flow}{Rate}\left( \frac{mL}{\min} \right)} = {\frac{{Volume}{Nebulised}({mL})}{{Time}{taken}({seconds})} \times 60{seconds}}$

TABLE 4 Table of flowrate achieved using aperture plates of Example 4 (NF = No Flow) Example 4 Example 4 Example 4 Device 1 Device 2 Device 2 Flowrate Flowrate Flowrate Solution ml/min ml/min Solution ml/min Saline 0.525 0.513 Purified 0.758 Water 5% 0.503 0.457 5% 0.792 Glycerol Ethanol 10% 0.471 0.457 10% 0.692 Glycerol Ethanol 20% 0.430 0.412 20% 0.546 Glycerol Ethanol 30% 0.372 0.358 30% 0.520 Glycerol Ethanol 40% 0.235 0.244 50% 0.496 Glycerol Ethanol 41% 0.213 0.228 70% 0.480 Glycerol Ethanol 1 42% 0.186 0.198 90% 0.502 Glycerol Ethanol 43% 0.169 0.200 100% 0.535 Glycerol Ethanol 44% 0.152 0.186 Glycerol 45% 0.142 0.178 Glycerol 46% 0.108 0.171 Glycerol 47% 0.104 0.129 Glycerol 48% 0.094 0.094 Glycerol 49% NF NF Glycerol

VMD

The effect of the increasing viscosity and reducing surface tension on the aerosol droplet size formation was then measured (n=3) and the results are shown below in Table 5. VMD is volume mean diameter which was measured using a Malvern Instrument Spraytec laser diffraction system. Ref FDA Guidance (1993): Reviewer Guidance for Nebulizers, Metered Dose Inhalers, Spacers and Actuators. Available from http://www.fda.gov/downloads/medicaldevices/deviceregulation andguidance/guidancedocuments/ucm081293.pdf;¹

TABLE 5 Table of measured VMD when glycerol solution are aerosolised using the aperture plates of Example 4. Example 4 Example 4 Device 1 Device 2 VMD measured VMD measured Solution (μm) (μm) Saline 3.216 3.610 5% 3.191 3.584 Glycerol 10% 3.143 3.474 Glycerol 20% 3.112 3.323 Glycerol 30% 3.118 3.329 Glycerol 40% 3.072 3.170 Glycerol 47% 3.004 3.098 Glycerol

Comparative Tests Example 5—Comparative

The results shown in Table 5, are the average flowrate (n=3) for increasing % w/w of Glycerol and % v/v of Ethanol for using the aperture plates of Example 5. Example 5 devices were manufactured from different wafers.

The measuring technique was as describe above.

TABLE 6 Table of flowrate using aperture plates of Example 5 (NF = No Flow) Example 5 Example 5 Example 5 Example 5 Example 5 Device 1 Device 2 Device 3 Device 4 Device 4 Flowrate Flowrate Flowrate Flowrate Flowrate Solution ml/min ml/min ml/min ml/min Solution ml/min Saline 0.512 0.456 0.492 0.353 Purified 0.574 Water 5% 0.478 0.489 0.492 0.346 5% 0.407 Glycerol Ethanol 10% 0.448 0.487 0.506 0.343 10% 0.361 Glycerol Ethanol 20% 0.375 0.425 0.444 0.276 20% 0.337 Glycerol Ethanol 30% 0.172 0.218 0.273 0.111 30% 0.311 Glycerol Ethanol 31% 0.238 0.083 0.281 0.223 40% NF Glycerol Ethanol 32% 0.221 NF 0.2421 0.205 50% Glycerol Ethanol 33% 0.184 0.227 0.188 70% Glycerol Ethanol 1 34% 0.150 0.199 0.153 90% Glycerol Ethanol 35% 0.124 0.173 0.125 100% Glycerol Ethanol 36% 0.113 NF NF Glycerol 40% NF Glycerol 50% Glycerol

VMD

The effect of the increasing viscosity and reducing surface tension on the aerosol droplet size formation using the aperture plates of Example 5 were then measured (n=3) and the results are shown below in Table 7. The measuring technique is as described above.

TABLE 7 Table of measured VMD with glycerol solution for aperture plates of Example 5 (NF = No Flow) Example 5 Example 5 Device 2 Device 4 VMD measured VMD measured (μm) (μm) Saline 5.902 4.049 5% 5.512 3.885 Glycerol 10% 5.367 3.754 Glycerol 20% 5.001 4.040 Glycerol 30% 4.764 NF Glycerol 34% 4.300 Glycerol

Note: In tables 5 and 7, the maximum detectable VMD were reported, There was flow observed with higher concentrations of Glycerol however the Malvern Instrument's Spraytec laser diffraction system was unable to detect the aerosolised droplet due to low aerosol density.

In summary, the aperture plates of comparative Example 5 fail to operate at % w/w Glycerol greater that 31-36% depending on device. This suggest that any viscous liquid formulation of drugs with viscosity >2.6-3.0 cP and surface tension of 71-72 mN/m will not nebulise using the aperture plates of Example 5.

The aperture plates of Example 4 (manufacture using photodefined technology) performed better when compared to the aperture plates of Example 5. It was found that the aperture plates of Example 4 could nebulise up to 48% w/w Glycerol which was the largest % Glycerol that was nebulised. In addition, the nebulisation of the 48% w/w Glycerol maintained a reasonable flowrate which was comparable with the comparative aperture plates of Example 5 at 30% w/w Glycerol. The aperture plates of Example 4 increase the maximum viscosity of the liquid that can be nebulised to ˜5.5-6.0 cP (an increase of ˜2-3 cP).

In all devices tested, the VMD of each device was seen to decrease as the viscosity increased and surface tension decreases. The larger the starting VMD of the device, the larger the decrease in VMD at the largest % Glycerol.

Existing technologies are not capable of nebulizing formulations in particular some commercially available surfactants that have viscosities >2 cP and surface tension <25 mN/m. Although there are some commercially available surfactants which are possible to nebulize, the performance of the existing nebulization technologies are sub-optimal in particular with regard to flow rates and droplet size.

An additional significant issue with existing technologies is the tendency to cause frothing and potentially de-naturing of the surfactant formulations as they were being nebulized.

Although this invention directly applies to surfactants, all formulations or excipients with similar physiochemical characteristics as those described will be readily nebulized using the technology described. For example, we have found that an antibiotic, Colistin, which has proved difficult to nebulize using existing electroplated mesh technology (˜10× slower than an aqueous based solution) can now be nebulized.

In addition, the technology allows for the generation of consistently smaller droplets than have heretofore been possible with conventional technologies. The ability to generate sub 2 micron and sub 3 micron droplets allows for sustained and maximal alveolar and onward systemic drug delivery of a wide variety of formulations including proteins, gene therapies, biological suspensions and surfactants.

The delivery of surfactants to neonates and all patient types that have a surfactant deficiency or requirement for surfactant is facilitated. Lung surfactant acts to increase pulmonary compliance, to prevent atelectasis (collapse of the lung) at the end of expiration and to facilitate recruitment of collapsed airways. Due to its physiochemical properties lung surfactant greatly reduces surface tension, increasing compliance allowing the lung to inflate much more easily, thereby reducing the work of breathing. It reduces the pressure difference needed to allow the lung to inflate.

The use of surfactants as a carrier for other drug types to enable penetration of these drugs into the lung utilising the low surface tension properties of surfactant is also facilitated.

Delivery of formulation types with specified physiochemical characteristics (i.e. lower surface tension and/or higher viscosity as compared to an aqueous solution) which have been difficult, i.e. slow delivery times, for existing mesh type nebulizers. e.g. Colistin (colistimethate sodium) is now facilitated.

TABLE 8 Example 4- VMD and Flowrates with Colistimethate sodium, Alveofact ®, Saline and Curosurf ® Surfactant VMD Flow rate Example 4 # (μm) (mL/min) Colistimethate sodium 4.154 0.519 Curosurf ® Surfactant 3.420 0.265 Alveofact ® Surfactant 3.032 0.500 Saline 2.227 0.520

The Example 4 devices performed well and nebulisation with Colistimethate sodium, Alveofact®, Curosurf® and saline was achieved. No flooding was observed and a strong plume was maintained throughout (See Table 8). The VMD results for previously problematic formulations for nebulization via vibrating aperture plates, range from 3.032-4.154 μm while maintaining a good flowrate ranging from 0.265-0.519. The viscosity and surface tension for Alveofact® Surfactant Colistimethate sodium, Alveofact® and Curosurf® are listed in Table 3.

The invention also allows the use of excipients or diluents with the specified physiochemical characteristics (i.e. lower surface tension and/or higher viscosity as compared to an aqueous solution) e.g. polysorbates, glycerol, polyethylene glycol, propylene glycol, butanediol, pluronics, Captisol, in amounts and concentrations that have not proved nebulizable to date in flow rates and/or at output rates that are clinically and commercially beneficial.

The treatment of pulmonary diseases with drugs that have not been nebulizable to date are now facilitated by the invention.

The use of the lungs as a pathway to systemic delivery of drugs that have not been nebulizable to date is also facilitated.

Generation of consistently small i.e. sub 2 and sub 3 micron particles is enabled which permits significantly increased systemic delivery of previously nebulizable formulations.

The treatment of surfactant specific diseases including (A)RDS, surfactant deficiency are enabled as are and less specifically treatment of patients with inhalation injury to the lung, prophylaxis by delivery of lung surfactant into patients at high risk for respiratory disease due to lung surfactant inactivation or injury to type II alveolar cell activity and treatment of obstructive syndromes of small airways.

Surfactant can be used as a vehicle for other drug actives. The use of surfactant and perfluorocarbons (another low surface tension formulation) aid in the post-deposition spreading on the lung surface.

Actives include viral and non-viral vectors as well as naked gene therapies for direct administration to the lung.

The technology provides at least some of the following advantages:

-   -   Nebulize formulations that have a viscosity >2 Cp.     -   Nebulize formulations that have a surface tension >0.5 mN/m.     -   Nebulize formulations that have a viscosity >2 cP combined with         a surface tension >0.5 mN/m.     -   Nebulize formulations that have a viscosity >2 cP combined with         a surface tension >60 mN/m.     -   Ability to nebulize formulations that have not previously been         nebulizable so as to increase the range of drug types that can         now be aerosolized and delivered to the lungs of all patient         types     -   Nebulization of surfactant type formulations     -   The technology is applicable to all delivery modes including         mechanically ventilated, non-invasive ventilation, off-vent,         nCPAP, high flow, and spontaneous breathing also.     -   Generate and maintain generation of very low droplet sizes with         surfactants and albuterol and other formulations intended for         systemic delivery. This is important as we do not need to filter         out larger particles through the use of baffles and the like and         that this manifests as ultra high fine particle (respirable)         fractions that concurrently maintain the integrity of the         formulation. We have demonstrated that surfactant retains it's         activity and physicochemical characteristics post nebulisation         using photodefined technology.     -   Ability to achieve high aerosol output rates. With classically         difficult to nebulise formulations (such as pulmonary         surfactants) we have achieved output rates at 0.33 mL/min and         above. Separately, we have recorded output rates in excess of 1         and 2 mL/min with simple solutions, e.g. saline and albuterol.         Such fast flow rates provide full control over the rate of         aerosolisation. For example, high flow rates can be tuned down         to very low output rates (which is sometimes desirable, e.g. PDE         inhibitors). The technological limitation experienced by         existing technology is that high aerosol output rates are not         achievable in the first place.

Any suitable medicament, therapeutic agent, active substance or pharmaceutically active compound than can be targeted to the lung may be employed.

Surfactant medications (sometimes referred to herein as “surfactants”) are protein-lipid compositions, e.g. phospholipids, that are produced naturally in the body and are essential to the lungs' ability to absorb oxygen. They facilitate respiration by continually modifying surface tension of the fluid normally present within the air sacs, or alveoli, that tube the inside of the lungs. In the absence of sufficient surfactant, these air sacs tend to collapse, and, as a result, the lungs do not absorb sufficient oxygen. Insufficient surfactant in the lungs results in a variety of respiratory illnesses in both animals and humans. Since most of these surfactant medications are animal-based, the current supply is limited, and although synthetic surfactants are available, their manufacture is currently both inexact and expensive. In addition, the surfactant medications are typically high in viscosity and are difficult to deliver to the patient's respiratory system. The combination of surfactant with other medicaments to improve distribution in the lung and body is also possible. Surfactants also possess the capacity to act as anti-adhesion agents.

The invention facilitates delivery in aerosol form of, for example, bronchodilators, including (3-agonists, muscarinic antagonists, epinephrine; surfactants; pain-relief medications including anaesthetics; migraine therapies; anti-infectives; anti-inflammatories, steroids, including corticostroids; chemotherapeutic agents; mucolytics; vasodilators; vaccines and hormones. In addition substances classified as anti-thrombogenic agents, anti-proliferative agents, monoclonal antibodies, anti-neoplastic agents, anti-mitotic agents, anti-sense agents, anti-microbial agents, nitric oxide donors, anti-coagulants, growth factors, translational promoter, inhibitors of heat shock proteins, biomolecules including proteins, polypeptides and proteins, oligonucleotides, oligoproteins, siRNA, anti-sense DNA and RNA, ribozymes, genes, viral vectors, plasmids, liposomes, angiogenic factors, hormones, nucleotides, amino acids, sugars, lipids, serine proteases, anti-adhesion agents including but not limited to hyaluronic acid, biodegradable barrier agents may also be suitable.

The medicament may for example, comprise long-acting beta-adrenoceptor agonists such as salmeterol and formoterol or short-acting beta-adrenoceptor agonists such as albuterol.

The medicament may be a long-acting muscarinic antagonists such as tiotropium (Spiriva) or short-acting muscarinic antagonists such as ipratropium (Atrovent).

Typical anti-infectives include antibiotics such as an aminoglycoside, a tetracycline, a fluoroquinolone; anti-microbials such as a cephalosporin; and anti-fungals. Examples of antibiotics include anti-gram-positive agents such as macrolides, e.g. erythromycin, clarithromycin, azithromycin, and glycopeptides, e.g. vancomycin and teicoplanin, as well as any other anti-gram-positive agent capable of being dissolved or suspended and employed as a suitable aerosol, e.g. oxazoldinone, quinupristin/dalfopristen, etc. Antibiotics useful as anti-gram-negative agents may include aminoglycosides, e.g. gentamicin, tobramycin, amikacin, streptomycin, netilmicin, quinolones, e.g. ciprofloxacin, ofloxacin, levofloxacin, tetracyclines, e.g. oxytetracycline, dioxycycline, minocycline, and cotrimoxazole, as well as any other anti-gram-negative agents capable of being dissolved or suspended and employed as a suitable aerosol.

Anti-inflammatories may be of the steroidal such as budesonide or ciclesonide, non-steroidal, such as sodium cromoglycate or biological type.

Typical local anaesthetics are, for example, Ropivacaine, Bupivacaine, levobupivacaine, and Lidocaine.

Chemotherapeutic agents may be alkylating agents, antimetabolites, anthracyclines, plant alkaloids, topoisomerase inhibitors, nitrosoureas, mitotic inhibitors, monoclonal antibodies, tyrosine kinase inhibitors, hormone therapies including corticosteroids, cancer vaccines, anti-estrogens, aromatase inhibitors, anti-androgens, anti-angiogenic agents and other anti-tumour agents.

The invention is not limited to the embodiments hereinbefore described which may be varied in detail. 

1. A method for aerosolising a liquid comprising the steps of:— providing an aperture plate having at least 100 outlet holes per mm²; delivering liquid to the aperture plate wherein the viscosity of the liquid is in the range of from 1 to 15 cP and the surface tension of the liquid is in the range of from 72 to 0.5 mN/m; and vibrating the aperture plate to produce an aerosol wherein the output rate of the generated aerosol is greater than 0.01 mL/min.
 2. A method as claimed in claim 1 wherein the fraction of the droplets which are less than 3 microns in size is greater than 75%, greater than 80%, greater than 85%, or greater than 90%.
 3. A method as claimed in claim 1 wherein the aperture plate has at least 500 outlet holes per mm², at least 1,000 outlet holes per mm², at least 1,500 outlet holes per mm², at least 2,000 outlet holes per mm², at least 2,500 outlet holes per mm², at least 3,500 outlet holes per mm², or at least 5,000 outlet holes per mm².
 4. A method as claimed in any of claims 1 to 11 wherein the volumetric median diameter of the droplets is less than 5 microns, less than 4 microns, less than 3 microns, less than 2.5 microns, less than 2.0 microns, less than 1.5 microns, or less than 1 microns.
 5. A method as claimed in any of claims 1 to 4 wherein the viscosity of the liquid is less than 12 cP, less than 10 cP, less than 7 cP, less than 5 cP, or less than 2 cP.
 6. A method as claimed in any of claims 1 to 5 wherein the surface tension of the liquid is less than 70 mN/m, less than 65 mN/m, less than 60 mN/m, less than 55 mN/m, less than 50 mN/m, less than 40 mN/m, less than 30 mN/m, less than 25 mN/m, less than 20 mN/m, less than 10 mN/m, less than 5 mN/m, or greater than 0.5 mN/m.
 7. A method as claimed in any of claims 1 to 6 wherein the output rate of the generated aerosol is greater than 0.05 mL/min, greater than 0.075 mL/min, greater than 0.1 mL/min, greater than 0.2 mL/min, greater than 0.3 mL/min, greater than 0.33 mL/min, greater than 0.5 mL/min, greater than 1.00 mL/min, or greater than 2.00 mL/min.
 8. A method as claimed in any of claims 1 to 7 wherein the liquid contains a medicament.
 9. A method as claimed in any of claims 1 to 7 wherein the liquid contains a surfactant.
 10. A method as claimed in any of claims 1 to 7 wherein the liquid contains a pharmaceutical. 